Modulating liquid pump

ABSTRACT

The present invention relates to a modulating liquid pump. This pump comprises an inlet port for receiving a liquid and an outlet port for delivering said liquid, an electromagnetic pump placed between the inlet port and the outlet port and comprising a piston for pumping said liquid, said modulating pump further including a regulating means, for regulating the pressure of the liquid. This pump is noteworthy in that said regulating means is of the electric type and is capable of regulating the travel of said piston according to an electrical setpoint signal (Vc). Application to fuel oil burners.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 12/670,845, which is the U.S. National Stage of InternationalPatent Application PCT/FR2008/001107, filed on Jul. 24, 2008. Throughthe '845 application the present application claims priority to FrenchPatent Application 0705462 filed on Jul. 26, 2007. Each of theaforementioned applications are encorporated by reference herein intheir entirety.

FIELD OF THE INVENTION

This invention relates to a modulating pump for liquid, in particularfor fuel oil.

BACKGROUND OF THE INVENTION

For illustrative purposes, this text will make reference to a modulatingpump intended for use with a fuel-oil burner. However, it is understoodthat the modulating pump according to the invention is not limited tothis particular use.

Fuel-oil burner manufacturers have long searched for a means of adaptingthe power of the burners to the actual heating requirements dependent onthe variations in the outdoor temperature.

Burners are known which are capable of operating at two powers referredto as low and high. Such a pump is disclosed in particular by thedocument EP 0 715 704. It comprises a pump with internal gearing whichis connected to a fuel-oil automation unit via a line kept at constantpressure by a pressure regulator and a three-way valve device. Thisdevice optionally connects the fuel-oil automation unit to either thepressure side or the return side of the pump so as to create a modulatedpressure. The valve device applies the constant pressure or themodulated pressure to the automation unit, thereby enabling the burnerto operate at two power levels.

However, the pumps equipping these burners cannot be operated in anintermediate mode between high power and low power.

Modulating burners are likewise known for medium and high powers, e.g.,from 1,000 to 30,000 kW, the fuel-oil spraying power of which isregulated continuously by acting on an adjusting screw of a pressureregulator. The document FR 2 241 746 describes such a burner. However,this type of regulation is not suited to low-power burners, due the costthereof and to the overall dimensions of same.

An electronically modulating pump is also known, such as the onedescribed in European Patent EP 0 202 714, comprising a pump body withan internal chamber, an intake channel, a discharge line provided with aone-way valve, a coil arranged around a first portion of the pump bodyand a partially magnetisable piston housed inside said chamber and heldin one position by a spring. By increasing the voltage at the coilterminals, the piston moves under the effects of the magnetic field, andthe fluid is discharged. By controlling the voltage frequency of thecoil, the discharge volume of the pump is varied. However, in this case,only the volume of fluid displaced is regulated and not the pressure.

SUMMARY OF THE INVENTION

The purpose of the invention is to easily enable a modulating pump to beoperated continuously between a minimum pressure and a maximum pressure.By continuous operation it is understood to mean that the outletpressure of the liquid can be controlled at any set pressure, betweenthe minimum pressure and the maximum pressure.

The invention is based on the use of an electromagnetic pump arranged ina modulating pump and on an electric control device for regulating thetravel of the piston of this electromagnetic pump.

The applicant has indeed observed that the pressure of the pressure ofthe liquid at the outlet of the modulating pump is a nearly linearfunction of the voltage of the electrical control signal applied to theelectromagnetic pump.

Thus, the object of the invention is a modulating liquid pump comprisinga inlet port for receiving a liquid and an outlet port for deliveringsaid liquid, an electromagnetic pump arranged between the inlet port andthe outlet port and comprising a piston for pumping said liquid, a meansof regulating the pressure of the liquid, said modulating pump beingcharacterised in that said regulating means is of the electric type andis capable of regulating the travel of said piston according to anelectrical setpoint signal.

The piston travel is advantageously controlled by the voltage level ofthe electrical setpoint signal.

According to a preferred embodiment, the regulating means is designed toapply a modulated electrical voltage signal to an excitation winding ofthe electromagnetic pump.

In particular, the regulating means is designed to receive analternating electrical voltage signal and may comprise a means ofrectifying this signal, e.g., a diode bridge if it is desired to rectifythe negative alternations, or a diode if it is desired to simplyeliminate the negative alternations.

According to one particular embodiment, the regulating means is capableof receiving an alternating electrical signal at a frequency of 50 Hz or60 Hz.

The modulating pump advantageously comprises an anti-backflow device forthe liquid between the inlet port and the outlet port.

In particular, the anti-backflow device can include an intake valvearranged upstream from the electromagnetic pump and a discharge valvearranged downstream from the electromagnetic pump.

According to one preferred embodiment, the modulating pump includes anadditional pumping means arranged between the inlet port and theelectromagnetic pump.

This additional pumping means is advantageously of the gear pump type.

The modulating pump can preferably include a means of regulating theminimum pressure and/or the maximum pressure of the liquid.

DESCRIPTION OF THE DRAWING

The invention will be better understood in light of the followingdescription, which is made for illustrative and non-limiting purposes,with reference to the single appended drawing in which a schematicrepresentation has been shown of a modulating pump according to theinvention for supplying a fuel-oil nozzle.

DESCRIPTION OF A PREFERRED EMBODIMENT

The modulating pump 2 includes an inlet port 4 intended to be connectedto a fuel-oil tank 6 and an outlet port 8 intended to be connected to anozzle 10.

An electromagnetic pump 12 is arranged between the inlet port and theoutlet port. This electromagnetic pump 12 conventionally includes anexcitation winding 14, which is intended to be powered by an electricalcontrol signal, a cylindrical armature 16 linked with a pump piston 18and a compression spring 20. The piston slides inside a cylinder 22which communicates with the intake via an intake valve 24 and with thedischarge via a discharge valve 26.

The applicant observed that, when the supply voltage on the excitationwinding 14 decreases, thereby resulting in a reduction in the travel ofthe piston 18, the pressure of the fuel oil likewise decreases in themodulating pump, and does so almost linearly.

More precisely, the supply voltage determines the piston travel, andconsequently the flow rate of the fuel oil pump by the piston and thusthe pressure of the fuel oil at the outlet port 8.

This supply voltage is a modulated voltage for driving the piston in aback-and-forth movement. It is provided with a regulating means 28 whichreceives an electrical setpoint signal Vc. The setpoint signal, forexample, is derived from an alternating voltage signal coming from theelectrical network at 50 Hz or 60 Hz, and the voltage of which isadjusted according to the desired fuel-oil pressure.

In the embodiment shown, the rectifying means 30 is a diode, whicheliminates the negative alternations of the signal Vc. It would likewisebe possible to rectify the negative alternations by means of a diodebridge. Finally, in certain applications, it is possible to apply thealternating signal directly to the excitation winding, if the frequencyof the alternating signal is chosen to be sufficiently low to enable thepiston to accomplish its back-and-forth movement thereof with thedesired amplitude, despite its inertia.

In certain applications, the electromagnetic pump 12 may have intakecapacity which alone is insufficient to enable proper operation of themodulating pump 2, in particular when the fuel-oil tank 6 is distantfrom the modulating pump 2, for example, when this distance is severalmeters. In this case, the modulating pump 2 advantageously includes anadditional pump 28, e.g., such as a gear pump, which is arrangedupstream from the electromagnetic pump and which is intended tosupplement the low intake capacity of the electromagnetic pump.

The modulating pump likewise further includes a minimum pressureregulator 34 and a maximum pressure regulator 36, upstream anddownstream from the electromagnetic pump, respectively, these regulatorsalso being connected to a discharge line 18 terminating in the tank 6.

As shown, on the discharge side of the electromagnetic pump 12, it mayfurther include a pressure sensor 38, a hydro-pneumatic accumulator 40,for smoothing out the fluctuations in pressure due to the back-and-forthmovement of the piston, and a solenoid safety shut-off valve 42.

1. Modulating liquid pump (2) comprising an inlet port (4) receiving a liquid and an outlet port (6) for delivering said liquid, an electromagnetic pump (12) arranged between the inlet port and the outlet port and comprising a piston (18) for pumping said liquid, said modulating pump comprising a means of regulating (28) the pressure of the liquid, characterised in that said regulating means (28) is of the electric type and is capable of regulating the travel of said piston (18) according to an electrical setpoint signal (Vc).
 2. Modulating pump of claim 1, characterised in that the travel of the piston (18) is controlled by the voltage level of the electrical setpoint signal (Vc).
 3. Modulating pump as claimed in one of the preceding claims, characterised in that the regulating means (28) is designed to apply a modulated electrical voltage signal to an excitation winding (14) of the electromagnetic pump (12).
 4. Modulating pump of claim 3, characterised in that the regulating means (28) is designed to receive an alternating electrical voltage signal and comprises a means of rectifying (30) this signal.
 5. Modulating pump as claimed in one of claims 3 or 4, characterised in that the regulating means (28) is capable of receiving an alternating electrical signal at a frequency of 50 Hz or 60 Hz.
 6. Modulating pump as claimed in one of the preceding claims, characterised in that it comprises an anti-backflow device (24, 26) for the liquid between the inlet port and the outlet port.
 7. Modulating pump of claim 6, characterised in that the anti-backflow device includes an intake valve (24) arranged upstream from the piston (18) of the electromagnetic pump (12) and a discharge valve (26) arranged downstream from the piston (18) of the electromagnetic pump (12).
 8. Modulating pump as claimed in one of the preceding claims, characterised in that it includes an additional pumping means (32) arranged between the inlet port (4) and the electromagnetic pump (12).
 9. Modulating pump of claim 10, characterised in that the additional pumping means is of the gear pump type.
 10. Pump as claimed in one of the preceding claims, characterised in that it includes a means of regulating (34, 36) the minimum pressure and/or the maximum pressure of the liquid. 